The present invention relates to a compressed air dusting gun and more specifically, to a gun which includes a pressure discharge valve oscillating within a predetermined frequency range.
The application of compressed air for removal of dirt and cleaning purposes is a well known and extensively used technique. In order to produce a concentrated and controllable air jet, the usual design includes a pistol-like tool equipped with an oblong air nozzle and a built-in shut-off valve. The shut-off valve is manually operated via a pawl or similar trigger mechanism mounted in connection with the handle of the dusting gun. When the trigger mechanism is activated, a concentrated air jet is discharged through the nozzle and by pointing this air jet on the object to be cleaned, it is possible to loosen and blast off foreign matter, such as dust, earth, oily coats. The ability of the air jet to loosen old dirt and adherent coatings of various kinds depends on the dynamic pressure exerted by the jet, i.e. primarily the jet velocity. The greater the velocity, the better the cleaning effect.
However, the jet velocity is limited to the available air pressure source, usually on the order of 6 bar, and consequently, an increase in the cleaning effect can only be achieved by increasing the air flow. Especially for the purpose of removal of adherent thick accumulations, the air consumption may easily be disproportionately large and the cleaning method therefore uneconomical.
DE Publication No. 1,099,760 (Odendahl) describes a known dusting gun for compressed air which consists of a valve designed with a longitudinally displaceable oblong valve body whose one end is in sealing contact against a valve seat shutting off the air flow through the gun under the influence of a compression spring, and whose other end is embodied as a piston, which is displaceably inserted into a closed cylinder. One side of the piston is in contact with the air duct in the dusting gun downstream of the valve via a longitudinal bore through the valve body and whose other side is in connection with the pressure side upstream of the valve through an adjustable regulator. The inlet to and the outlet from the dusting gun are shaped as a Laval nozzle. The regulator may be adjusted so that the movement of the piston is in resonance with the natural frequency of the pressure column in the system.
This known dusting gun is complicated in its construction. It is difficult to adjust and the velocity of the air is oscillating in a region from somewhat below to somewhat above the Mach region.